Just came across an interesting challenge: I was trying to warp an object that was positioned almost diagonal (about 35º).
This emerged as a challenge for the current warp system (or quite possibly my understanding and use of it): it's exclusively aimed at horizontal and vertical warping.
When you set warp points, they form a grid that has a mainly horizontal and vertical focus which meant fudging to get the distortion I was looking for. Instead of being able to rotate the warp grid basis and just tweak what I wanted, I had to rotate the image first, warp what I wanted and then rotate it back.
I know that warping and mesh are mainly aimed at perspective corrections (hence the horizontal/vertical focus), but adding some form of rotation of that base orientation could offer interesting new possibilities.
(and yes, I'd love to see this in AD too, but one thing at a time ;) ).